C.J. Burgoyne
Department of Engineering, University of Cambridge,
Cambridge, UK
I. Balafas
Tony Gee and Partners, Surrey, UK
Most of the technical problems associated with the use of fibre reinforced plastics
(FRPs) have been addressed; they offer a good technical solution to the
problems of corrosion of reinforcement. However, apart from the use of glued-on
CFRP strips for flexure, fibre reinforced plastics (FRPs) are not finding their way into
mainstream use. The reason is economic, since the first cost of the materials
is higher than steel and the discount rates used to produce NPV mean that
future repair costs have negligible effect now. Industry’s perception is that fibre reinforced plastics
(FRPs) are uneconomic for newly-built structures, so they are not used.
In this paper the true cost of steel corrosion is addressed, using realistic
models for chloride and water ingress, traffic delay costs and realistic repair
costs; an appropriate discount rate is also discussed. These models are applied
to the survey of 257,000 bridges in the US and predictions are made for the
money that could be saved if future bridges were built using non-corroding fibre reinforced plastics
(FRPs). Unlike present calculations which (conveniently for the
politicians) show that cheapest first cost is also the cheapest whole-life
cost, the results show that additional money spent now on improving the
durability of structures is a very sound investment.
Steel corrosion threatens the durability of concrete
structures and vast, and increasing, budgets are currently spent for repair.
The use of fibre
reinforced plastic (FRP) in concrete is one of the alternative methods
to address the problem of corrosion. Even though research has been extensive in
the last two decades, applications are only met in prototype structures.
Industry hesitates to consider those materials as an alternative to steel due
to its high price. In this paper methods to study the economics of those
materials are presented and conclusions on their viability in bridges are
drawn. For their assessment both the initial and the life cycle costs are
considered.
References
Broomfield, J. P., Corrosion of Steel in Concrete, 1st edition, E&FN Spon,
1997.
United States Federal Highway
Administration, Recording and Coding
Guide for the Structure Inventory and Appraisal of the Nation’s Bridges, Report
number: FHWA-PD-96-001, 2002.
The Department of Transport – UK, Evaluation
of Maintenance Costs in Comparing Alternative Designs for Highway Structures,
Advice notice, 2002.
Nelson, W., Accelerating Testing: Statistical Models, Test Data and Data Analysis,
1st edition, Willey Interscience, 1990.
Balafas, I, Fibre-Reinforced-Polymers versus Steel in Concrete Bridges: Structural
Design and Economic Viability, PhD thesis, University of Cambridge,
October 2003.
Wallbank, E. J., The Performance of Concrete Bridges: A
Survey of 200 Highway Bridges, HSMO, London, Department of Transport, UK
– G. Maunsell & Partners, 1989.
Balafas, I and Burgoyne, C.J.,
“Optimal Cost Design for Beams Prestressed with FRP Tendons,” Fibre-Reinforced
Plastics for Reinforced Concrete Structures (FRPRCS-6), Singapore,
2, 2003, pp 1391-1400.
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